Dynamic Network Configuration

ABSTRACT

Disclosed is a wireless communication system comprising a plurality of antennas, a plurality of base stations, each base station being adapted to connect to one or more of the antennas over an available spectrum, and a wireless switching module. The wireless switching module is adapted to allocate one or more portions of the available spectrum to each antenna dependent on a compatibility constraint on the antennas, and assign each antenna for connection to a base station.

FIELD

The present invention is related to wireless communication and inparticular to resource allocation for wireless network communication,including spectrum and infrastructure resources.

BACKGROUND

Spectrum is a scare resource in wireless communication systems, and isoften poorly utilized. In conventional wireless networks, spectrumallocation is fixed (non-adaptive) during network planning anddeployment, based on statistical characteristics of previous measuredtraffic. However, in practice, wireless traffic occurs in bursts, over anumber of different time scales. As such, the conventional fixedallocation approach that does not adapt to traffic dynamics leads topotentially large durations when significant spectrum is underutilized,or even unused.

In existing indoor wireless networks, spectral utility (the ratio ofusage to allocation) is particularly low for two reasons. Firstly,indoor deployment is traffic-oriented rather than coverage-oriented (asin outdoor networks), and a large amount of spectral resources areallocated for the expected traffic peaks. Secondly, interference cannotbe coordinated due to the complicated indoor environments, andorthogonal spectrum allocation is therefore extensively employed. As aresult, more spectrum and more infrastructure such as base stations areallocated than are truly necessary to handle the wireless traffic.

In conventional outdoor wireless networks, such as cellular and sensornetworks, spectral utility is also relatively low. Resources such asspectrum and base stations are typically allocated to fixed,uniformly-sized cells to provide seamless coverage. However, the users'spatial distribution and consequently the spatial distribution oftraffic are not uniform between cells. As such, the conventionalapproach of fixed cell allocation leads to an underuse of resources atsome sparsely populated cells while also often failing to satisfy thetraffic requests in other, heavily populated cells. This results in theinefficient utilization of spectrum, and the effective system capacityis low.

SUMMARY

Disclosed are arrangements which, seek to address one or more of theabove problems by enabling a wireless network to dynamically allocateresources, including spectrum and base stations, so as to adapt totemporally and geographically varying traffic patterns.

According to a first aspect of the present disclosure, there is provideda wireless communication system comprising: a plurality of antennas; aplurality of base stations, each base station being adapted to connectto one or more of the antennas over an available spectrum; and awireless switching module adapted to allocate one or more portions ofthe available spectrum to each antenna dependent on a compatibilityconstraint on the antennas, and assign each antenna for connection to abase station.

According to a second aspect of the present disclosure, there isprovided a method of dynamically configuring a wireless communicationsystem comprising a plurality of antennas and a plurality of basestations, each base station being adapted to connect to one or more ofthe antennas over an available spectrum. The method comprises allocatingone or more portions of the available spectrum to each antenna; andassigning each antenna for connection to a base station, wherein theallocating is dependent on a compatibility constraint on the antennas.

According to a third aspect of the present disclosure, there is provideda device in a wireless communication system comprising a plurality ofantennas and a plurality of base stations, each base station beingadapted to connect to one or more of the antennas over an availablespectrum, the device being adapted to allocate one or more portions ofthe available spectrum to each antenna dependent on a compatibilityconstraint on the antennas, and assign each antenna for connection to abase station.

A beneficial result of the disclosed arrangements is that when a largeamount of bandwidth requests occur in an area, more base stations areconnected to the antennas serving that area, thereby allocating morespectrum and processing capability. Meanwhile, fewer base stations areconnected to the antennas providing coverage for low-traffic areas.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described with reference to thedrawings, in which:

FIG. 1 is a block diagram of a bidirectional wireless communicationsystem;

FIGS. 2A and 2B collectively form a schematic block diagramrepresentation of an electronic device as which the wireless switchingmodule in FIG. 1 may be implemented;

FIG. 3 is a flow chart illustrating a method of adaptively configuringthe system of FIG. 1;

FIG. 4 is a flow chart illustrating a method of allocating spectrum toantennas, as used in the method of FIG. 3;

FIG. 5 is a flow chart illustrating a method of assigning antennas tobase stations, as used in the method of FIG. 3;

FIG. 6 is a flow chart illustrating a method of assigning unassignedantennas to base stations, as used in the method of FIG. 5;

FIG. 7 is a flow chart illustrating a method of allocating furtherspectrum to unsatisfied antennas, as used in the method of FIG. 3; and

FIG. 8 is a flow chart illustrating a method of allocating channels tobase stations, as used in an alternative implementation of the method ofFIG. 3.

DETAILED DESCRIPTION

Where reference is made in any one or more of the accompanying drawingsto steps and/or features, which have the same reference numerals, thosesteps and/or features have for the purposes of this description the samefunction(s) or operation(s), unless the contrary intention appears.

FIG. 1 is a block diagram of a′ bidirectional wireless communicationsystem 100 according to one embodiment. The system 100 comprises N basestations 110-1, 110-2, . . . , 110-N, each of which is a source of andsink for an associated one of the in-phase and quadrature (I-Q) signals,e.g. 115.

The term “base station” as used in this disclosure refers to a basebandand radio frequency (RF) signal processing unit. There are two types ofbase station, defined by their relationship to the wireless spectrumavailable for use by the wireless communication system 100. One typeonly sends and receives signals within a portion, or channel, of theavailable spectrum; for example, an FDMA (frequency division multipleaccess) processing unit. Therefore, multiple base stations of this typeare needed to cover the whole spectrum and still more base stations areneeded for channel reuse. The other type of base station sends andreceives signals across the whole available spectrum, for example, anOFDMA (orthogonal frequency division multiple access) processing unit.Multiple base stations of this type are needed to be able to employchannel reuse, although fewer than for the first type. A channel may beof variable width and comprises one or more FDMA carriers or OFDMAsubcarriers.

The system 100 also comprises K antennas 130-1, 130-2, . . . , 130-K,each of which is a source of and sink for signals, e.g. 125, that areprocessed to/from the signals 115 associated with the base stations110-n by an associated amplifier/filter 140-i. The antennas 130-iconvert those signals from/to signals received/transmitted wirelessly.Each antenna 130-i can transmit and receive signals on multiple channelssimultaneously. However, the spatial arrangement of the antennas 130-imeans that certain antennas cannot transmit/receive on the same channelwithout mutual interference. Such antennas are termed “incompatible”.

The base stations 110-n are connected to the antennas 130-i via awireless switching module 120, which is able to route signals from/toany base station 110-n to/from any antenna 130-i.

The wireless switching module 120 is connected to an Operation andMaintenance Centre (OMC) device 150, which is a standard-independentserver.

The signals 115 between the wireless switching module 120 and the basestations 110-n may be either RF or digital baseband signals. The signals125 between the wireless switching module 120 and the antennas 130-i areRF signals.

The wireless switching module 120 executes a method, to be describedbelow, that configures the routing of signals within the system 100dynamically between configuration intervals, dependent on bandwidthrequirements associated with each antenna 130-i during eachconfiguration interval. A typical configuration interval is of the orderof a few minutes.

The antennas 130-i are fixed in location. Assuming each antenna 130-iserves a specific area relative to the antenna location, the wirelessswitching module 120 computes a bandwidth requirement associated witheach antenna 130-i for each configuration interval as described below.

The dynamic configuration of the system 100 by the wireless switchingmodule 120 has the effect that when a large amount of bandwidth requestsoccur in an area, more base stations 110-n (up to a maximum of one perantenna) are connected to the antennas 130-i serving that area, therebyallocating more spectrum and processing capability. Meanwhile, fewerbase stations 110-n are connected to the antennas 130-i providingcoverage for low-traffic areas. If each base station is identified witha “cell” of the wireless communication system 100, the areas covered bythe cells are therefore dynamically defined in response to varyingwireless traffic distribution.

The dynamic, or adaptive, configuration of the system 100 by thewireless switching module 120 allows the system 100 to operate in a moreresource-efficient way than conventional wireless networks. That is,given the same resources as a conventional system, more traffic can behandled, or conversely, fewer resources are needed to handle a givenload of traffic requests. In addition, adaptive configurationsignificantly decreases manual efforts required for network maintenanceand upgrades. The adaptive architecture can reduce the overall powerconsumption of the system 100 as a result of efficient allocation ofresources.

In alternative arrangements, the base stations 110-n in the system 100are operated by different telecommunications carriers. The antennas130-i associated with a given carrier are connected to a base station110-n operated by that carrier. In such arrangements, reconfiguration ofthe system 100 by the wireless switching module 120 takes place inresponse to a change in circumstances, such as one or more antennaschanging their carrier association to a different telecommunicationscarrier.

FIGS. 2A and 2B collectively form a schematic block diagram of a generalpurpose electronic device 201 including embedded components, as whichthe wireless switching module 120 may be implemented. As seen in FIG.2A, the electronic device 201 comprises an embedded controller 202.Accordingly, the electronic device 201 may be referred to as an“embedded device”. In the present example, the controller 202 has aprocessing unit (or processor) 205 which is bi-directionally coupled toan internal storage module 209. The storage module 209 may be formedfrom non-volatile semiconductor read only memory (ROM) 260 andsemiconductor random access memory (RAM) 270, as seen in FIG. 2B. TheRAM 270 may be volatile, non-volatile or a combination of volatile andnon-volatile memory.

As seen in FIG. 2A, the electronic device 201 also comprises a switchingdevice 210, which is coupled to the processor 205 via a connection 212.The switching device 210, controlled by the processor 205, is adapted tojoin connections 211 to connections 212 in any order. In the case of thewireless switching module 120, the connections 211 come from the basestations 110-n and the connections 212 come from the antennas 130-i.

As seen in FIG. 2A, the electronic device 201 also comprises a portablememory interface 206, which is coupled to the processor 205 via aconnection 219. The portable memory interface 206 allows a complementaryportable memory device 225 to be coupled to the electronic device 201 toact as a source or destination of data or to supplement the internalstorage module 209. Examples of such interfaces permit coupling withportable memory devices such as Universal Serial Bus (USB) memorydevices, Secure Digital (SD) cards, Personal Computer Memory CardInternational Association (PCMIA) cards, optical disks and magneticdisks.

The electronic device 201 also has a communications interface 208 topermit coupling of the device 201 to a computer or communicationsnetwork 220 via a connection 221. The connection 221 may be wired orwireless. For example, the connection 221 may be radio frequency oroptical. An example of a wired connection includes Ethernet. Further, anexample of wireless connection includes Bluetooth™ type localinterconnection, Wi-Fi (including protocols based on the standards ofthe IEEE 802.11 family), Infrared Data Association (IrDa) and the like.

The methods described hereinafter may be implemented as one or moresoftware application programs 233 executable within the embeddedcontroller 202. The electronic device 201 of FIG. 2A implements thedescribed methods. In particular, with reference to FIG. 2B, the stepsof the described methods are effected by instructions in the software233 that are carried out within the controller 202. The softwareinstructions may be formed as one or more code modules, each forperforming one or more particular tasks.

The software 233 of the embedded controller 202 is typically stored inthe non-volatile ROM 260 of the internal storage module 209. Thesoftware 233 stored in the ROM 260 can be updated when required from acomputer readable medium. The software 233 can be loaded into andexecuted by the processor 205. In some instances, the processor 205 mayexecute software instructions that are located in RAM 270. Softwareinstructions may be loaded into the RAM 270 by the processor 205initiating a copy of one or more code modules from ROM 260 into RAM 270.Alternatively, the software instructions of one or more code modules maybe pre-installed in a non-volatile region of RAM 270 by a manufacturer.After one or more code modules have been located in RAM 270, theprocessor 205 may execute software instructions of the one or more codemodules.

The application program 233 is typically pre-installed and stored in theROM 260 by a manufacturer, prior to distribution of the electronicdevice 201. However, in some instances, the application programs 233 maybe supplied to the user encoded on one or more CD-ROM (not shown) andread via the portable memory interface 206 of FIG. 2A prior to storagein the internal storage module 209 or in the portable memory 225. Inanother alternative, the software application program 233 may be read bythe processor 205 from the network 220, or loaded into the controller202 or the portable storage medium 225 from other computer readablemedia. Computer readable storage media refers to any storage medium thatparticipates in providing instructions and/or data to the controller 202for execution and/or processing. Examples of such storage media includefloppy disks, magnetic tape, CD-ROM, a hard disk drive, a ROM orintegrated circuit, USB memory, a magneto-optical disk, flash memory, ora computer readable card such as a PCMCIA card and the like, whether ornot such devices are internal or external of the device 201.

Examples of computer readable transmission media that may alsoparticipate in the provision of software, application programs,instructions and/or data to the device 201 include radio or infra-redtransmission channels as well as a network connection to anothercomputer or networked device, and the Internet or Intranets includinge-mail transmissions and information recorded on Websites and the like.A computer readable medium having such software or computer programrecorded on it is a computer program product.

FIG. 2B illustrates in detail the embedded controller 202 having theprocessor 205 for executing the application programs 233 and theinternal storage 209. The internal storage 209 comprises read onlymemory (ROM) 260 and random access memory (RAM) 270. The processor 205is able to execute the application programs 233 stored in one or both ofthe connected memories 260 and 270. When the electronic device 201 isinitially powered up, a system program resident in the ROM 260 isexecuted. The application program 233 permanently stored in the ROM 260is sometimes referred to as “firmware”. Execution of the firmware by theprocessor 205 may fulfil various functions, including processormanagement, memory management, device management, storage management anduser interface.

The processor 205 typically includes a number of functional modulesincluding a control unit (CU) 251, an arithmetic logic unit (ALU) 252and a local or internal memory comprising a set of registers 254 whichtypically contain atomic data elements 256, 257, along with internalbuffer or cache memory 255. One or more internal buses 259 interconnectthese functional modules. The processor 205 typically also has one ormore interfaces 258 for communicating with external devices via systembus 281, using a connection 261.

The application program 233 includes a sequence of instructions 262though 263 that may include conditional branch and loop instructions.The program 233 may also include data, which is used in execution of theprogram 233. This data may be stored as part of the instruction or in aseparate location 264 within the ROM 260 or RAM 270.

In general, the processor 205 is given a set of instructions, which areexecuted therein. This set of instructions may be organised into blocks,which perform specific tasks or handle specific events that occur in theelectronic device 201. Typically, the application program 233 waits forevents and subsequently executes the block of code associated with thatevent. Events may be triggered in response to input from a user, via theuser input devices 213 of FIG. 2A, as detected by the processor 205.Events may also be triggered in response to other sensors and interfacesin the electronic device 201.

The execution of a let of the instructions may require numeric variablesto be read and modified. Such numeric variables are stored in the RAM270. The disclosed method uses input variables 271 that are stored inknown locations 272, 273 in the memory 270. The input variables 271 areprocessed to produce output variables 277 that are stored in knownlocations 278, 279 in the memory 270. Intermediate variables 274 may bestored in additional memory locations in locations 275, 276 of thememory 270. Alternatively, some intermediate variables may only exist inthe registers 254 of the processor 205.

The execution of a sequence of instructions is achieved in the processor205 by repeated application of a fetch-execute cycle. The control unit251 of the processor 205 maintains a register called the programcounter, which contains the address in ROM 260 or RAM 270 of the nextinstruction to be executed. At the start of the fetch execute cycle, thecontents of the memory address indexed by the program counter is loadedinto the control unit 251. The instruction thus loaded controls thesubsequent operation of the processor 205, causing for example, data tobe loaded from ROM memory 260 into processor registers 254, the contentsof a register to be arithmetically combined with the contents of anotherregister, the contents of a register to be written to the locationstored in another register and so on. At the end of the fetch executecycle the program counter is updated to point to the next instruction inthe system program code. Depending on the instruction just executed thismay involve incrementing the address contained in the program counter orloading the program counter with a new address in order to achieve abranch operation.

Each step or sub-process in the processes of the methods to be describedbelow is associated with one or more segments of the application program233, and is performed by repeated execution of a fetch-execute cycle inthe processor 205 or similar programmatic operation of other independentprocessor blocks in the electronic device 201.

There are two scenarios at which the embodiments of the invention aredirected. In Case I, antennas 130-i connected to a common base station110-n cannot transmit or receive in the same channel. In Case II,antennas 130-i connected to a common base station 110-n can transmit orreceive in the same channel.

Conventional indoor distributed antenna systems are an example of CaseII, where each base station outputs multiple replicas of identical radiofrequency signals to multiple antennas in the downlink by using asplitter. In the uplink, the base station receives a combination of RFsignals from these antennas. The connections between base stations andantennas are conventionally fixed when the systems are deployed, andfrequencies are configured manually. Therefore no capability of dynamictraffic load balancing is available.

To implement adaptive connection between base stations 110-n andantennas 130-i, and adaptive allocation of channels, within conventionalsystems, the following constraints are confronted in terms ofcompatibility with commercial base station devices.

-   -   For commercial base station devices, the only available output        from and input to the wireless switching module 120 should be RF        signals.    -   The wireless switching module 120 and methods carried out        thereby should be independent of standards and base station        devices, especially hardware.    -   A Case II base station 110-n cannot compute the bandwidth        requirement of each antenna 130-i if multiple antennas 130-i are        connected to it in the same channel, because the base station        processes the combined signals from the multiple antennas.

The architecture of the wireless switching module 120 depends on thedeployment scenario. In Case I, in which antennas connected to a commonbase station exclusively occupy particular channels, there are threeapproaches, depending on the type of base station in use:

-   -   1. (FDMA base stations) The wireless switching module 120        comprises a filter for each antenna 130-i. Each antenna 130-i        receives or transmits on a subset of the FDMA carriers allocated        to its connected base station 110-n.    -   2. (FDMA or OFDMA base stations) The wireless switching module        120 comprises an extra radio frequency module and a digital        processing module. Therefore, the wireless switching module 120        is able to convert the signals from the base stations 110-n to        baseband (digital baseband for OFDMA systems or analogue        baseband for FDMA systems), and regenerate antenna-specific        signals according to the configured connections and channel        allocation.    -   3. (OFDMA base stations) The wireless switching module 120        comprises the RF part and the inverse fast-Fourier transform        part of the digital processing. In this approach the signals 115        are digital (baseband) signals. The wireless switching module        120 is thus capable of dispatching particular OFDMA subcarriers        to a certain antenna 130-i. This architecture may become a        standard indoor network element, either industrial standard or        vendors' product specification.        Identical methods of allocating antenna-specific channels and        connecting base stations 110-n to antennas 130-i apply to the        three approaches for Case I. In approaches 1 and 2, no hardware        modification is imposed on commercial base stations.

In Case II, the wireless switching module 120 connects base stations110-n to antennas 130-i and determines the allocation of channels foreach base station 110-n. Once the antennas 130-i and base stations 110-nare connected, the wireless switching module 120 replicates and routesRF signals between base stations 110-n and antennas 130-i. Becausesignals from a base station 110-n are broadcast to all of its connectedantennas 130-i, the update of the connections between base stations andantennas is transparent to the schedulers in the base stations (or otherupper layer network elements). No change is needed to commercial basestation devices, either in hardware or software.

FIG. 3 is a flowchart illustrating a method 300 of adaptivelyconfiguring the system 100 of FIG. 1 according to one embodiment. Themethod 300 is carried out by the wireless switching module 120 at thestart of each configuration interval. The method 300 is suitable forCase I base stations.

The method 300 starts at step 305 where the wireless switching module120 determines a K-by-K compatibility matrix CM defined by thegeographical locations of antennas 130-i. The compatibility matrix CMencapsulates the compatibility constraints of the antennas 130-i. Sincethe antennas 130-i are fixed in location, step 310 need only be carriedout once and the compatibility matrix CM stored for use in subsequentpasses through the method 300 for as long as the antennas 130-i remainfixed.

The (i,j)-th entry of the compatibility matrix CM depends on whetherantennas 130-i and 130-j are compatible, i.e. can transmit/receive inthe same channel without interference. If they can, CM(i,j)=1;otherwise, CM(i,j)=0.

Next, at step 310, the wireless switching module 120 computes abandwidth requirement amount r_(i) (i=1, . . . , K) associated with eachantenna 130-i for the current configuration interval.

The implementation of step 310 depends on the deployment scenario. UnderCase I, each antenna 130-i exclusively occupies particular channels ofits connected base station for both transmitting and receiving. The OMCdevice 150 is thus able to identify the channels and therefore theassociated antennas the bandwidth requests come through. The wirelessswitching module 120 uses this information to compute the bandwidthrequirements of each antenna 130-i.

Under Case II, due to RF signal combining, a base station 110-n cannotidentify the channels a particular antenna 130-i connected to it isusing. Two types of information are gathered to compute the antennas'bandwidth requirements:

-   -   The wireless switching module 120 obtains base station-specific        bandwidth requirement values from the OMC device 150.    -   If multiple antennas 130-i are connected to a common base        station 110-n, the wireless switching module 120 measures each        antenna's receiving power. (Given a power spectrum density (PSD)        of received signals, which is usually stable due to power        control, the total power is proportional to the bandwidth        requirement.)

The two types of information are processed jointly by the wirelessswitching module 120 to compute the antenna-specific bandwidthrequirement amounts r_(i).

At the following step 320, the wireless switching module 120provisionally allocates spectrum to the antennas 130-i for the currentconfiguration interval based on the compatibility constraints on theantennas 130-i and the bandwidth requirement r_(i) associated with eachantenna 130-i for the current configuration interval. The method carriedout at step 320 will be further described below with reference to FIG.4.

The method 300 then proceeds to step 330 at which the wireless switchingmodule 120 downscales the provisional spectrum allocations made at step320 to ensure the available bandwidth is not exceeded. In the followingstep 340, the wireless switching module 120 assigns each antenna 130-ifor connection to one base station 110-n based on the provisionalspectrum allocations to each antenna 130-i. The method carried out atstep 340 will be further described below with reference to FIG. 5.

At the next step 350 of the method 300, the wireless switching module120 allocates spectrum to any antenna(s) 130-i that are not fullysatisfied, i.e. do not have sufficient provisionally allocated spectrumto satisfy the associated bandwidth requirements. The method carried outat step 350 will be further described below with reference to FIG. 7.Finally, at step 360, the wireless switching module 120 allocatesspectrum to each base station 110-n based on the spectrum allocated toeach antenna 130-i assigned to that base station 110-n in the previoussteps 310 to 350. The configuration of the system 100 is then completeand the method 300 concludes.

FIG. 4 is a flow chart illustrating a method 400 of provisionallyallocating spectrum to antennas 130-i, as carried out by the wirelessswitching module 120 in step 320 of the method 300 of FIG. 3. The inputsto the method 400 are the compatibility matrix CM and the bandwidthrequirement amount r_(i) (i=1, . . . , K) associated with each antenna130-i. The aim of the method 400 is to maximise the satisfaction of thebandwidth requirements r_(i), subject to the compatibility constraintson the antennas 130-i and the available bandwidth.

The method 400 begins at step 410, where certain variables areinitialised: a channel counter k to 1, a matrix CM, to CM, and residualbandwidth requirements r_(k,i) to r_(i) (i=1, . . . , K). The matrixCM_(k) defines a compatibility graph CMG wherein each node represents anantenna 130-i, and an edge exists between two antennas 130-i and 130-jif they are compatible, i.e. CM(i,j)=1. At the next step 420, thecliques c_(j) of the compatibility graph CMG defined by CM_(k) areconstructed. A clique c_(i) is a subset of the vertices of CMG (orequivalently, a subset of the set of integers {1, . . . , K}) such thateach pair of vertices in the clique c_(i) are connected by an edge inCMG. The antennas 130-i represented by the nodes in each clique c_(i)are all mutually compatible.

The method 400 then proceeds to step 430, at which the wirelessswitching module 120 determines the largest clique c_(k), and sets aprovisional allocation amount b_(k) to the minimal residual requirementr_(k,i) over the chosen clique c_(k):

$b_{k} = {\min\limits_{i \in c_{k}}r_{k,i}}$

An amount of spectrum equal to b_(k) in channel k is provisionallyallocated to all antennas in the chosen clique c_(k). At the next step440, new residual requirements r_(k+1i) are determined as follows:

$r_{{k + 1},i} = \left\{ \begin{matrix}{{r_{k,i} - b_{k}},{i \in c_{k}}} \\{r_{k,i}\mspace{14mu} {otherwise}}\end{matrix} \right.$

That is, the residual requirement r_(k,i) for each antenna 130-i in thechosen clique c_(k) is reduced by the provisional allocation amountb_(k), while the residual requirements for the other antennas remainunchanged. At least one antenna 130-i in the chosen clique c_(k) therebyhas its residual requirement r_(k,i) reduced to zero.

Step 450 follows, at which a new compatibility matrix CM_(k+1) isdetermined by removing from CM_(k) each row and column corresponding toan antenna that is fully satisfied, i.e. whose residual requirementr_(k,i) has reached zero. Because there must be at least one suchantenna 130-i in every iteration k, CM_(k+1) must be smaller thanCM_(k).

At step 460, it is determined whether CM_(k+1) is null, i.e. contains norows or columns. If so, the method 400 concludes (470); otherwise, themethod 400 increments k (step 480) and returns to step 420 for the nextiteration. At the end of the method 400, all antennas 130-i are fullysatisfied, and the number k of iterations, which is the number ofchannels containing provisionally allocated bandwidth, is denoted asK_(W).

The outcome of the step 320 is the list of chosen cliques c_(k) and acolumn vector b of provisional allocation amounts b_(k) in each channelk=1, . . . , K_(W). Defining a K_(W)-by-K binary “occupation matrix” Csuch that each row k has K binary entries indicating which antennas130-i belong to the clique c_(k), the i-th column v_(i) (the “channeloccupation vector” of antenna 130-i) of C indicates occupation ofchannels 1 to K_(W) by the corresponding antenna 130-i.

Step 320 provisionally allocates spectrum to antennas regardless of theavailable bandwidth in each channel. In step 330, the wireless switchingmodule 120 downscales the provisionally allocated spectrum vector b bydividing b by the “utilisation ratio” ratio U, defined as the totalbandwidth provisionally allocated in the step 320 to the total availablebandwidth B, if the utilisation ratio is larger than 1:

$U = \frac{\sum\limits_{k = 1}^{K_{W}}b_{k}}{B}$

The satisfaction ratio P_(i) is defined for each antenna 130-i as theratio of provisionally allocated spectrum to the bandwidth requirementassociated with that antenna 130-i:

$P_{i} = {\frac{1}{r_{i}}b^{T}v_{i}}$

Before the downscaling step 330, the satisfaction ratio P_(i) was equalto one for all antennas 130-i. After the downscaling step 330, thesatisfaction ratio P_(i) may have been reduced (by U), but is still thesame for all antennas 130-i. The wireless switching module 120 hastherefore maximised the minimal satisfaction ratio P_(i) across allantennas 130-i within the available bandwidth B regardless of connectionconstraints between base stations 110-n and antennas 130-i. However,each antenna 130-i can only be connected to one base station 110-n.According to the Case I scenario, multiple antennas 130-i can beconnected to one base station 110-n if their spectrum allocations do notconflict, i.e. if at most one antenna 130-i is allocated spectrum ineach channel. In the step 340, the wireless switching module 120 assignsantennas to base stations so as to satisfy these “connectionconstraints” arising from the spectrum allocations resulting from step320.

FIG. 5 is a flow chart illustrating a method 500 of assigning antennas130-i to base stations 110-n, as carried out by the wireless switchingmodule 120 in step 340 of the method 300 of FIG. 3. The method 500begins at step 510, where the wireless switching module 120 constructs aK-by-K connectivity matrix CN that encapsulates the connectionconstraints mentioned above. The (i,j)-th entry in CN indicates whetherantennas 130-i and 130-j can be connected to the same base station:

${{CN}\left( {i,j} \right)} = \left\{ \begin{matrix}{1,} & {{{if}\mspace{14mu} v_{i}^{T}v_{j}^{T}} = 0} \\{0,} & {otherwise}\end{matrix} \right.$

If CN(i,j) is one, antennas 130-i and 130-j (or their channel occupationvectors v_(i) and v_(j)) are said to be orthogonal, and therefore can beconnected to the same base station.

Next, at step 520, a base station counter n is initialised to one. Inthe following step 530, the cliques c_(j) of a connectivity graph CNGdefined by the connectivity matrix CN are constructed in similar fashionto step 420 of method 400. Each clique c_(j) indicates a subset ofantennas 130-i whose provisional spectrum allocations are mutuallyorthogonal and can therefore be connected to the same base station110-n.

As a side note, the connectivity graph CNG is almost complementary tothe compatibility graph CMG. This because incompatible antennas must beallocated orthogonal spectrum, so no edge in CMG implies an edge in CNG.However, compatible antennas can also be allocated orthogonal spectrum(if their common clique is never chosen in step 430), so an edge in CMGdoesn't imply no edge in CNG.

Step 540 follows, at which the wireless switching module 120 chooses theclique c_(n) with the maximum amount of allocated bandwidth:

$c_{n} = {\underset{c_{j}}{argmax}\left( {b^{T}{\sum\limits_{i \in c_{j}}^{\;}{v_{i}(k)}}} \right)}$

At the next step 550, the group of antennas 130-i corresponding to thechosen clique c_(n) is assigned for connection to the base station110-n. At step 560, the rows and columns corresponding to the antennas130-i in the chosen clique c_(n) are removed from the connectivitymatrix CN. Step 570 tests whether the connectivity matrix CN is null. Ifso, all antennas 130-i have been assigned to a base station 110-n′ andthe method 500 concludes (599). In this case, all antennas are assignedto base stations such that each antenna 130-i has an spectrum allocationthat is orthogonal to all other antennas allocated to the same basestation 110-n.

However, such an ideal scenario does not always occur. If CN is notnull, step 575 tests whether n has reached the number N of basestations. If not, n is incremented (step 580) and the method 500 returnsto step 530 to reconstruct the cliques from the reduced connectivitymatrix CN. If so, the number N of base stations 110-n has been exhaustedand there remain some unassigned antennas 130-j, where jεΩ⊂{1, . . . ,K}. This non-ideal scenario is more likely if there are fewer antennapairs with orthogonal spectrum allocations, which in turn is more likelyif there are more compatible antenna pairs. In this case, the method 500proceeds to step 590, at which the unassigned antennas 130-j areassigned to base stations 110-n. Step 590 will be described in moredetail below with reference to FIG. 6.

FIG. 6 is a flow chart illustrating a method 600 of assigning unassignedantennas 130-j, where jεΩ, to base stations 110-n, as used in step 590of the method 500 of FIG. 5. Unassigned antennas 130-j cannot beorthogonal to any of the groups of antennas already assigned forconnection to respective base stations 110-n. The aim of the method 600is therefore to find the base station 110-n _(j) for each unassignedantenna 130-j that maximises the provisional spectrum allocation for thebase station 110-n _(j), which means finding the base station 110-n _(j)for each unassigned antenna 130-j such that the antenna 130-j is “mostorthogonal” to the other antennas 130-i connected to that base station110-n. To do this, the method 600 starts at step 610 by choosing thenext unassigned antenna 130-j, where jεΩ. At step 620, a base stationcounter n is initialised to one. Step 630 follows, at which the amountof spectrum Q that would be allocated to the base station 110-n if theto antenna 130-j were assigned to it is calculated:

${Q\left( {n,j} \right)} = {b^{T}{\max\left( {{\sum\limits_{i \in c_{n}}v_{i}},v_{j}} \right)}}$

At step 640, the method 600 tests whether n has reached the number N ofbase stations. If not, n is incremented (step 645) and the method 600returns to step 630. Otherwise, at step 650 the method 600 chooses n_(j)so as to maximise Q(n,j) for the current value of j. The antenna 130-jis assigned for connection to the corresponding base station 110-n _(j).Step 660 follows, at which the method 600 determines whether anyunassigned antennas 130-j remain in the set Ω. If so, the method 600returns to step 610. If not, the method 600 concludes (670).

Recall that Case I base stations cannot share channels between assignedantennas. Since the effect of step 590 is that one or more channels areshared between antennas 130-j for jεΩ and antennas 130-i alreadyassigned to the assigned base stations 110-n _(j), in step 595 theshared channels are subdivided into sub-bands.

In step 595, the wireless switching module 120 subdivides the channelsoccupied by antennas 130-i assigned to the base stations 110-n _(j) soas to maximise the minimal satisfaction ratio P_(i) across all thoseantennas. (Note that the satisfaction ratios P_(i) of antennas 130-iassigned to base stations 110-n not assigned to any antenna 130-j forjεΩ by the method 600 remain unchanged, so no adjustments are made bystep 595 to antennas 130-i assigned to those base stations.)

In step 595, the set of antennas 130-i assigned to the base station110-n _(j) is defined as Φ(n_(j)). Also, an adjusted, “fractional”occupation vector x_(i) is defined for each antenna 130-i assigned to abase station 110-n _(j). The fractional occupation vector x_(i) issubject to the constraints that

0≦x _(i)(k)≦1,k=1, . . . ,K _(W)

and

${\sum\limits_{i \in {\Theta {(n_{j})}}}x_{i}} = {\max\limits_{i \in {\Theta {(n_{j})}}}\left( v_{i} \right)}$

A non-integer entry x_(i)(k) in a fractional occupation vector x_(i)represents a subdivision of the corresponding channel k into sub-bandswith width proportional to the value of x_(i)(k). The above constraintsensure that the fractional occupation vectors x_(i) at a base station110-n _(i) only have non-zero entries in channels already occupied bythe antennas 130-i, iεΦ(n_(j)), assigned to that base station, and inthose occupied channels k, the occupation vector entries x_(i)(k) sum toone. This ensures that the total bandwidth of the spectrum allocation isnot increased by the step 595, and the compatibility constraints are notviolated.

To maximize the minimal satisfaction ratio over all antennas 130-iassigned to the base stations 110-n _(j), all the antennas 130-iassigned to each base station 110-n _(j) should have their satisfactionratios P_(i) as close to each other as possible.

The adjusted occupation vectors x_(i)* for the antennas 130-i assignedto the base station 110-n _(j) are therefore computed in step 595 as

${x_{i}^{*}:{i \in {\Theta \left( n_{j} \right)}}} = {\underset{x_{i}}{argmin}{\sum\limits_{m \in {\Theta {(n_{j})}}}\left( {{\frac{1}{r_{m}}b^{T}x_{m}} - {\frac{1}{r_{i}}b^{T}x_{i}}} \right)^{2}}}$

subject to the above constraints.

The adjusted occupation vectors x_(i)* may be obtained using variousconventional optimisation methods, such as the gradient method.

The maximal minimal satisfaction ratio P_(c) across all the antennas130-i assigned to the base stations 110-n _(j) can then be obtained asfollows:

$P_{c} = {\min\limits_{j \in \Omega}{\min\limits_{i \in {\Theta {(n_{j})}}}\left( {\frac{1}{r_{i}}b^{T}x_{i}^{*}} \right)}}$

In the optimal case, all the antennas 130-i assigned to a base station110-n _(j) have the identical satisfaction ratio P_(i). The upper boundof the maximal minimal satisfaction ratio P_(c) can thus be obtained asfollows:

$P_{c}^{Upper} = {\min\limits_{{({n_{j},j})},{j \in \Omega}}\left( \frac{{Pb}^{T}{\max\left( {{\sum\limits_{i \in c_{n_{j}}}v_{i}},v_{j}} \right)}}{b^{T}\left( {{\sum\limits_{i \in c_{n_{j}}}v_{i}} + v_{j}} \right)} \right)}$

where P is the aggregate satisfaction ratio defined as

$P = \frac{\sum\limits_{k = 1}^{K_{w}}b_{k}}{\sum\limits_{i = 1}^{K}r_{i}}$

After step 595 is completed, the occupation vectors v_(i) in theoccupation matrix C are replaced by the fractional occupation vectorsx_(i)* for iεΦ(n_(j)) and jεΩ.

After step 595, the method 500 concludes (599).

If after step 340 the satisfaction ratio P_(i) is less than 1 for anyantenna 130-i, its bandwidth requirement r_(i) remains unsatisfied. Instep 350 of the method 300, the wireless switching module 120 allocatesfurther spectrum to any unsatisfied antennas 130-i such that nointerference is introduced between incompatible antennas that areassigned to different base stations 110-n. This is accomplished byoperating on the channel occupation matrix C as described in more detailbelow with reference to FIG. 7.

FIG. 7 is a flow chart illustrating a method 700 of allocating furtherspectrum to unsatisfied antennas, as used in step 350 of the method 300of FIG. 3. In the method 700, the wireless switching module 120traverses the occupation matrix C row-by-row from top to bottom. Themethod 700 starts at step 710 where a row counter k is initialised. Atthe following step 720, the current row, i.e. row k, of the occupationmatrix C is assigned to a vector c_(k). Step 730 checks whether thecurrent row is the subset of one of the upper rows (in other words, somek′<k exists such that c_(k)′−c_(k) is non-negative in all entries). Ifso, more bandwidth can be allocated to the antenna 130-i correspondingto the column i that has a zero in the current row k and a positivevalue in the upper row k′. Step 740 therefore identifies such an i.

If the identified antenna 130-i has a non-zero fractional occupationentry x_(i)*(k) in channel k derived from the adjustment step 595, nofurther bandwidth is allocated to the identified antenna 130-i inchannel k, and the method 700 proceeds to step 770, as indicated by thedashed arrow in FIG. 7.

Otherwise, at the next step 750, the further allocated bandwidth andupdated bandwidth requirement for the antenna 130-i are respectivelycomputed as

r _(k,i)=min(r _(i) −b ^(T) v _(i) ,b _(k))

and

r _(i) =r _(i) −r _(k,i)

Next, at step 760, the occupation vector v_(i) for the antenna 130-i isupdated by replacing its k-th element (which, like c_(k)(i), has a valueof zero) with r_(k,i)/b_(k). Following step 760, or if no such k′ wasfound at step 730, the next step 770 checks whether k has reached K_(W).If not, at step 780 the value of k is incremented and the method 700returns to step 720. If so, the method 700 concludes (790).

In the final step 360 of the method 300, the wireless switching module120 allocates spectrum to each base station 110-n based on the spectrumallocated to the antennas 130-i assigned to that base station, asencapsulated in the occupation matrix C and the vector b.

Consider the available commercial Case II base stations that output theradio frequency signals. All the antennas 130-i, iΦ(n), assigned to aCase II base station 110-n by the wireless switching module 120 arereceiving and broadcasting identical radio frequency signals comprisingall channels allocated to these antennas. There is no need for anysubdivision of channels into sub-bands, and the total bandwidth for thebase station 110-n is

$b^{T}{\sum\limits_{i \in {\Theta {(n)}}}^{\;}{v_{i}.}}$

However, this combined broadcast is likely to violate the antennacompatibility constraints. An alternative implementation of the method300 suitable for Case II base stations therefore omits the adjustmentstep 595 from the method 500 and replaces the allocation step 350 withthe method 800, described below with reference to FIG. 8, in order toallow Case II base stations to satisfy the antenna compatibilityconstraints.

FIG. 8 is a flow chart illustrating a method 800 of allocating channelsto base stations, as used in place of step 350 in an alternativeimplementation of the method 300. The method 800 starts at step 810where a channel counter k is initialised to one. Denote Ω_(j,k) to bethe set of antennas 130-i connected to the base station 110-j andoccupying the current channel k. For channel k, among all the m_(k) basestations 110-j satisfying

${\sum\limits_{i \in \Omega_{j,k}}{v_{i}(k)}} > 0$

(or in other words with an assigned antenna occupying channel k, i.e.Ω_(j,k)≠Φ)), one or more base stations 110-j are to be selected tooccupy the channel k, and the other base stations and their assignedantennas will not use the channel k. To implement this, in step 820 anm_(k)×m_(k) base station compatibility matrix, M_(k), is constructed toindicate if any two base stations can occupy the channel k. To constructM_(k)

-   -   If CM(x,y)=0 for some xεΩ_(j,k) and yεΩ_(j,k), set M_(k)(i,j)=0        to indicate that the antennas connected to the base stations i        and j are not allowed to occupy the same channel.    -   If CM(x,y)=1 for all xεΩ_(i,k) and yεΩ_(j,k), set M_(k)(i,j)=1        to indicate that the antennas connected to the base stations i        and j are allowed to occupy the same channel.

The next step 830 constructs the cliques based on M_(k) and chooses thelargest clique c_(k). The base stations 110-j in the clique c_(k) andall the antennas 130-i assigned to those base stations are selected tooccupy the current channel k. The base stations 110-j not belonging tothe chosen clique c_(k) and the antennas assigned to those base stationsshould not occupy the channel k. So in step 840, the k-th elements ofthe channel occupation vectors v_(i) are set to zero for the antennas130-i assigned to the base stations 110-j not belonging to the chosenclique c_(k).

In step 850, the method 800 tests whether k has reached K_(W). If not,the method 800 increments the channel counter k at step 860 and returnsto step 820. Otherwise, the method 800 concludes (870).

The method 800, as part of the alternative implementation of the method300, ensures that the compatibility constraints are not violated betweenantennas connected to different base stations. All antennas connected toa base station achieve an identical satisfaction ratio that is basestation specific, and therefore the minimal satisfaction ratio isobtained by comparing those of all base stations.

By means of the adaptive configuration method 300, the wirelessswitching module 120 configures the wireless communication system 100 soas to maximise the minimal satisfaction ratio over all antennas 130-iunder the constraints of the compatibility of antennas, the fixed numberof bases, and the total amount of bandwidth available. In other words,the method 300 dynamically optimises the “proportional fairness” of thesystem 100, in that the ratio of allocated bandwidth to requiredbandwidth is kept as even as possible across all antennas 130-i, subjectto the above constraints.

The following is a non-exhaustive list of example applications of thedisclosed arrangements.

1. Support of Multi-Operator Networks

-   -   Property owners provide infrastructure-switching modules,        antennas and cables connecting them, and operate and maintain        the networks.    -   Multiple operators provide base station devices.    -   Operators share the frequencies in a licensed band and users.

The disclosed arrangements significantly reduce the property owners'dependency on the particular operators, especially when increasingcapacity and improving coverage, and also reduce the operators'investment expenditure.

2. Support of Multi-Vendor Infrastructures Usually, vendors are asked toprovide network planning and deployment on behalf of operators—thisleads to operators' and property owners' dependency on the vendors. Withno need of vendor-specific network planning, the base station devicesprovided by different vendors are able to coexist in a network accordingto the disclosed arrangements.

3. Support of Multiple Licensed Bands and Multiple Networks

-   -   Each antenna has a wide bandwidth covering multiple licensed        bands.    -   Each band corresponds to a network logically independent of the        others.    -   Either single- or multi-operator solution applies.    -   Independent network reconfiguration is carried out at each        licensed band.

The foregoing describes only some embodiments of the present invention,and modifications and/or changes can be made thereto without departingfrom the scope and spirit of the invention, the embodiments beingillustrative and not restrictive.

1. A wireless communication system comprising: a plurality of antennas;a plurality of base stations, each base station being adapted to connectto one or more of the antennas over an available spectrum; and awireless switching module adapted to allocate one or more portions ofthe available spectrum to each antenna dependent on a compatibilityconstraint on the antennas, and assign each antenna for connection to abase station.
 2. A wireless communication system according to claim 1,wherein the allocation is further dependent on bandwidth requirementsassociated with the respective antennas.
 3. A wireless communicationsystem according to claim 2, wherein the wireless switching module isfurther adapted to compute the bandwidth requirements from a receivedpower from each antenna.
 4. A method of dynamically configuring awireless communication system comprising a plurality of antennas and aplurality of base stations, each base station being adapted to connectto one or more of the antennas over an available spectrum, the methodcomprising: allocating one or more portions of the available spectrum toeach antenna; and assigning each antenna for connection to a basestation, wherein the allocating is dependent on a compatibilityconstraint on the antennas.
 5. The method of claim 4, wherein theallocating is further dependent on bandwidth requirements associatedwith the respective antennas.
 6. The method of claim 5, wherein theallocating comprises: choosing a largest mutually compatible subset ofthe antennas; provisionally allocating an amount of spectrum in achannel of the available spectrum to the antennas in the chosen subsetdependent on the bandwidth requirements of those antennas; removing atleast one antenna that is fully satisfied by the provisionally allocatedspectrum; and repeating the choosing, provisional allocating, andremoving for each channel until all bandwidth requirements aresatisfied.
 7. The method of claim 6, further comprising downscaling theprovisional spectrum portion allocations depending on the totalbandwidth of the available spectrum.
 8. The method of claim 4, whereinthe assigning comprises: assigning one or more antennas for connectionto base stations such that the antennas assigned to each base stationhave orthogonal spectrum allocations; and assigning each unassignedantenna for connection to a base station so as to maximise the spectrumallocation of the assigned base station.
 9. The method of claim 8,wherein the first assigning comprises: choosing a largest subset of theantennas whose spectrum allocations are mutually orthogonal; assigningthe antennas in the chosen subset for connection to a base station;removing the assigned antennas; and repeating the choosing, theassigning, and the removing for each base station or until all antennashave been assigned.
 10. The method of claim 8, wherein the secondassigning comprises, for each unassigned antenna: choosing the basestation that would maximise the amount of allocated spectrum if theunassigned antenna were assigned to that base station; and assigning theunassigned antenna for connection to the chosen base station.
 11. Themethod of claim 4, further comprising, after the second assigning,subdividing the channels occupied by the antennas assigned to basestations to which the second assigning assigned antennas so as tomaximise the minimal satisfaction ratio over those antennas.
 12. Themethod of claim 11, wherein the subdividing comprises: subdividing thechannels so that the antennas assigned to base stations to which thesecond assigning assigned antennas have satisfaction ratios as close toeach other as possible.
 13. The method of claim 4, further comprisingallocating further portions of the available spectrum to each antennathat does not have sufficient allocated spectrum to satisfy theassociated bandwidth requirement.
 14. The method of claim 4, furthercomprising allocating portions of the available spectrum to basestations dependent on the assignments of antennas to base stations. 15.The method of claim 4, further comprising allocating portions of theavailable spectrum to base stations dependent on assignments of antennasto base stations and the compatibility constraint.
 16. A device in awireless communication system comprising a plurality of antennas and aplurality of base stations, each base station being adapted to connectto one or more of the antennas over an available spectrum, the devicebeing adapted to allocate one or more portions of the available spectrumto each antenna dependent on a compatibility constraint on the antennas,and assign each antenna for connection to a base station.
 17. A deviceaccording to claim 16, wherein the allocating is further dependent onbandwidth requirements associated with the respective antennas.